Am I Overprotective? 😬

I have a 3 week old baby and a 4 1/2 year old stepdaughter. All of the grandmas are always telling the 4 year old to kiss on my baby and I don’t like it. I feel like she’s 4 and her hands and mouth are dirty and carry germs. I don’t think her hands and mouth should be all over my baby but I don’t know what to say. I don’t want to be a bitch. Am I being ridiculous or should i say something?

Update: Just wanted to add that MIL had my stepdaughter feel her soft spot and was telling her about it but never told her she should be careful or not touch it. She was encouraging her to rub it. I don’t feel like that’s a good idea... She’s only four. What if she pushes too hard? 😐